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""" Challenge 158 Task 2 """
from sympy import isprime
def get_eq(y: int, incr: int) -> float:
"""Solve the Cuban prime equation"""
# warning - waste here, it is ready also for the second series, even though we were
# not asked for it. This is a bad practice and one of the 7 wastes, but I just
# accept that I am aware of it and leave it.
x = y + incr
return (x**3 - y**3) / (x - y)
def get_cuban_primes(limit: int) -> list:
"""Do the exercise"""
primes = []
result = 0.0
y = 0
# it would be probabl safer to keep running for a while even after we get over the limit...
# maybe next values from the function(s) could drop again below the limit
# but it passes the test and I am a lazy programmer to check the actual outputs from
# the function, so let's just leave it ;)
while result <= limit:
y += 1
result = get_eq(y, 1)
if result != int(result):
continue
if isprime(int(result)):
primes.append(int(result))
return primes
assert get_cuban_primes(1000) == [7, 19, 37, 61, 127, 271, 331, 397, 547, 631, 919]
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